<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      #box{
        color: white;
      }
    </style>
  </head>
  <body>
    <div id="box" style="color: red">hello div</div>
    <script>
      const box = document.getElementById("box");

      box.style.border = "1px solid ";
      box.style.fontSize = "2rem";
      box.style["background-color"] = "gray";

      console.log(box.style.color);

      setTimeout(() => {
        box.style.color = "";
      }, 3000);
    </script>
  </body>
</html>
